The orderly transport of proteins through the secretory pathway of eukaryotic cells is mediated by the recognition of donor membrane-derived vesicles with distinct target organelles. The specificity of this interaction is mediated in part by the specific interaction of membrane proteins termed SNAREs. Our laboratory is identifying novel SNAREs that regulate protein transport in an attempt to understand the molecular basis of protein traffic and exocytosis in lymphocytes. We also interested in understanding the cell biology of T cell activation. We are examining the trafficking and localization of T cell ligands on antigen presenting cells both within these cells as well as on their plasma membranes. These studies are focused on understanding the molecular events leading to vesicular traffic, vesicle fusion with the plasma membrane, and the role of plasma membrane lipid microdomains in T cell activation.